Consonant sounds are perceived categorically. Listeners are consistently poor in discriminating the allophones which constitute a phonemic category. A recent study suggests that one might be able to train allophonic discrimination by systematically exposing listeners to the critical discriminant cue in isolation prior to speech discrimination testing. If so, perception theory might be elaborated to account for the independent contributions of phonemic and auditory processors, and a method of facilitating discrimination is second language teaching might be developed. This project proposes to train the discrimination of synthetic /r/-/l/ tokens in Japanese natives by requiring pre-exposure to the critical third formant, not typically heard as speech when presented in isolation, followed by a gradual phasing in of the first and second formants which make the composite structure speech-like. Analyses will examine Japanese discrimination across an equal-interval /r/-/l/ continuum and the discrimination of Americans within their /r/ and /l/ categories particularly.